Emergency hospital admissions rise following heavy rainfall after a new study found consumers’ drinking water can be contaminated by the release of untreated wastewater, increasing the risk for gastrointestinal illness."Combined" sewer systems collect both sewage and stormwater runoff on the way to treatment facilities. When heavy rainfall fills these systems beyond their capacity, untreated wastewater can back up into homes. To reduce the risk of home flooding during heavy precipitation, municipalities often discharge some of the untreated flow into nearby bodies of water.